JPH11352513A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent crosstalks generated from being caused by a capacity coupling existing between a pixel electrode and a signal line. SOLUTION: A reflection pixel electrode 50a and not only a signal line 27a but also another adjacent signal line 27b partially face opposite an insulating film to be capacitely coupled. Then, the size of the area of a part 27a1 , in which the signal line 27a is opposed to the reflection pixel electrodes 50a, is roughly equal to the size of the area of a part 27b2 in which the signal line 27b faces opposite a reflection pixel electrodes 50a. Consequently, the effects given on the reflection pixel electrodes 50a by the capacity coupling by the signal potential of the signal line 27a becomes roughly equal to the effects imparted on the reflected pixel electrodes 50a by the capacity coupling by the signal potential of the signal line 27b and luminance differences between adjacent electrodes 50a and 50b and between adjacent electrodes 50b, 50c and so on are relaxed, and the crosstalks are prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art FIG.
0 is a plan view, and FIG. 5 shows a vertical cross section along the line BB in FIG. This device includes an array substrate 110 on which thin film transistors (hereinafter, referred to as TFTs) 114 as switching elements are arranged in a matrix, a counter substrate 130 on which a light-transmitting counter electrode 136 is formed, and a And a liquid crystal layer 150 interposed therebetween.

[0003] On the array substrate 110, a plurality of TFTs 1 arranged in the row direction and arranged in the same direction.
A scanning line 113 in which fourteen gates are connected in common, and a plurality of scanning lines 113 arranged in a column direction orthogonal to the scanning line 113, and a signal in which one of the source and drain terminals of the TFT 114 arranged in this direction is connected in common The line 119 is wired. The other terminal of the TFT 114 forms a capacitor for storing a signal with the signal storage capacitor line 116 via an insulating film, and is connected to a reflective pixel electrode 120 described later via a contact 125.

An organic insulating layer 118 is formed on the scanning line 113, the signal line 119, the storage capacitor line 116, and the upper surface of the TFT 114. On the upper surface of the organic insulating layer 118, a reflective pixel electrode is provided corresponding to each pixel. 120 are formed.

On the counter substrate 130, a color filter 134 and a common electrode 136 are laminated on the surface of the substrate 132. The color filter 134 has a red, blue,
It has a configuration in which green colors are arranged. Then, an optical film 188 such as a retardation plate or a polarizing plate is attached to a surface of the substrate 132 opposite to the liquid crystal layer 150.

As described above, the reflection type liquid crystal display device 100 has:
A reflective pixel electrode 120 is provided above the TFT 114 and the signal storage capacitor line 116 via the organic insulating layer 118. Thus, the area where light incident from above in the drawing is reflected by the reflective pixel electrode 120 can be increased, and as a result, a bright image can be displayed in a dark place without a backlight.

[0007]

However, the conventional liquid crystal display has the following problems. As shown in FIG. 6A, when the raster window 302 is displayed on the green halftone background 301, vertical crosstalk occurs at the end of the window 302. In FIG. 4, since the reflection pixel electrode 120 and the signal line 119 are opposed to each other with the organic insulating layer 118 interposed therebetween, they are in a capacitively coupled state. However, the signal line 119 capacitively coupled to a certain pixel electrode 120
Represents one signal line 11 connected to the pixel electrode 120
9 only.

For this reason, even if the green halftone background 301 is supposed to display the same green color, the raster window 30
2 and a pixel 303 adjacent to the raster window 3
02 and the pixel 304 at a position away from the signal line 1
19 has a different effect on the pixel electrode 120 due to capacitive coupling. That is, in the pixel 304 vertically adjacent to the raster window 302, the raster window 30
Since the signal potential for displaying No. 2 is applied to the signal line 119, the signal potential is affected via the capacitive coupling.

Here, as shown in FIG. 5A, a voltage VP1 is applied to the pixel 303 under the influence of the raster window 302, and an original voltage VP0 is applied to the pixel 304. I do. Pixel 303 and pixel 3 in this case
03, the temporal change of the pixel potential respectively applied to
As shown in FIG.

The voltages VP1 and VP0 can be expressed as follows. The halftone signal potential is Vsg, the black signal potential is Vsb, and the signal potential for raster window display is Vsw. Further, a coupling ratio between a certain pixel and a signal line connected to the pixel via a TFT is Pco, and a coupling ratio between an i-th signal line adjacent to the signal line and the pixel is Pci. I do. VP0 = Vsg (1) VP1 = Vsg + Pc0 (Vsb-Vsg) + Pc1 (Vsw-Vsg) + Pc2 (Vsb-Vsg) + Pc3 (Vsw-Vsg) + ... = Vsg + (Pc0 + Pc2 + PC4 + c + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc + Pc) ) (Vsw−Vsg) (2) As a result, the pixel electrode 120 and the pixel 3 in the pixel 303
Since the effective voltage differs from that of the pixel electrode 120 in 04 and a luminance difference occurs, crosstalk occurs. Such a problem also occurs in a transmission type liquid crystal display device.

The present invention has been made in view of the above circumstances, and has as its object to provide a liquid crystal display device capable of preventing crosstalk.

[0012]

According to the liquid crystal display device of the present invention, pixel electrodes each having a switching element are arranged in a matrix on a substrate, and a plurality of signal lines are arranged in a column direction. An array substrate in which the switching elements are commonly connected to the signal lines, a counter substrate arranged to face the array substrate, and a light-transmitting counter electrode provided on the substrate, the array substrate and the counter substrate Each signal line is alternately covered with a pixel electrode connected to the signal line and a pixel electrode connected to a different signal line along the column direction. It is characterized by being.

Further, the pixel electrode may be an opaque reflective electrode.

Alternatively, in the liquid crystal display device of the present invention, pixel electrodes each having a switching element are arranged in a matrix on a substrate, and a plurality of signal lines are arranged in a column direction.
An array substrate in which the switching element is commonly connected to each of the signal lines for each column, a counter substrate disposed to face the array substrate, and a light-transmitting counter electrode provided on the substrate; A liquid crystal layer sandwiched between the substrate and the counter substrate, wherein each pixel electrode overlaps with a plurality of signal lines, and a region of the signal line overlapped with the pixel electrode has an entire width of the signal line. It is a region that includes.

Here, the total width of the signal line is the length of the signal line in a direction orthogonal to the column direction.

It is preferable that the area where each signal line overlaps the pixel electrode is substantially equal.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a horizontal cross-sectional structure of the liquid crystal display device according to the present embodiment, and FIG. 2 shows a vertical cross-sectional structure along the line AA in FIG. This device 200
Are TFTs 30a, 30b, 3
, 300a, 300b, 300c,... Are arranged in a matrix, an opposing substrate 80 on which a translucent opposing electrode 54 is formed, and sandwiched between these substrates 20 and 80. And a liquid crystal layer 90.

A plurality of array substrates 20 are arranged on the substrate 22 along a row direction (horizontal direction in the figure), and the TFTs 30a, 30b, 30 are arranged along the same direction.
, 300a, 300b, 300c,..., and a plurality of scanning lines 24, 240... which are connected in common, and a plurality of scanning lines are arranged in a column direction (vertical direction in FIG. Signal lines 27a, 27b,
27c,... Are arranged. Here, the signal line 27
are connected to one of the source and drain terminals of the TFTs 30a, 300a..., and the signal line 27b is connected to the TFT 30a.
One terminal of the TFTs 30c, 300c,... is commonly connected to the signal line 27c. TFTs 30a, 30b, 30c,
, 300a, 300b, 300c,... Constitute a storage capacitor with the signal storage capacitor line 26 via an insulating film, and further, via a contact 27, a pixel electrode 50a, 50b, 50c described later. , ..., 500a, 500
, 500c,...

More specifically, the TFTs 30a, 30b, 3
, 300a, 300b, 300c,... Have a semiconductor layer in which a channel region is formed, and low-resistance semiconductor layers located at both ends thereof and ohmic-connected to source and drain electrodes. A source electrode and a drain electrode are connected on the low-resistance semiconductor layer, and one of the electrodes is connected to the pixel electrodes 50 a, 50 b, and 50 through a contact hole 29.
,..., 500a, 500b, 500c,.

The scanning lines 24, 240,..., The signal lines 27a,
27b, 27c,..., TFTs 30a, 30b, 30c,
, 300a, 300b, 300c,..., A not-shown protective film is formed on the upper surface, and an organic insulating layer 118 made of, for example, an acrylic resin is formed on the upper surface of the protective film. On the upper surface of the organic insulating layer 118, the reflection pixel electrodes 50a, 50b, 50c,.
a, 500b, 500c,... are formed. Reflective pixel electrodes 50a, 50b, 50c, ..., 500a, 500
are formed of a material having a high reflectivity, such as silver, aluminum, or an alloy thereof, so as to reflect external light incident from above in the drawing.

In the counter substrate 80, a color filter 52 and a common electrode 54 are laminated on the surface of a substrate 132. The color filter 52 has a configuration in which red, blue, and green colors are arranged for each pixel. On the surface of the substrate 132 opposite to the liquid crystal layer 90, an optical film 188 such as a retardation plate or a polarizing plate is attached. A liquid crystal layer 90 is sandwiched between the array substrate 20 and the counter substrate 80. As the liquid crystal layer 90, for example, a material such as a nematic liquid crystal can be used.

The TFT 30 provided on the array substrate 20
The reflective pixel electrodes 50a, 50b,.
Is switched for each pixel.
External light incident from above in the figure via the counter substrate 80 is reflected by the reflective pixel electrodes 50a, 50b,.
The transmittance is controlled by the liquid crystal layer 90 for each pixel, and a predetermined image is formed.

Unlike the conventional devices shown in FIGS. 4 and 5, in this embodiment, the reflective pixel electrodes 50a, 50a
0b, 50c, ..., 500a, 500b, 500c, ...
The two signal lines are arranged below each of the layers through the organic insulating layer 118 so as to face each other. For example, not only the portion 27a1 of the signal line 27a corresponding to this pixel but also the portion 27b2 of the signal line 27b corresponding to an adjacent pixel faces the reflective pixel electrode 50a. Not only the portion 27b1 of the signal line 27b corresponding to this pixel but also the portion 27c2 of the signal line 27c corresponding to the adjacent pixel faces the reflective pixel electrode 50b. Furthermore, the area of the portion 27a1 of the signal line 27a facing the reflective pixel electrode 50a is substantially the same as the area of the portion 27b2 of the signal line 27b, and similarly, the area of the portion 27b1 of the signal line 27b facing the reflective pixel electrode 50b. Area and signal line 27
The area of the portion 27c2 of c is substantially the same.

By wiring in this manner, the insulating film 118 is formed.
Through the respective reflective pixel electrodes 50a, 50b, 50
, 500a, 500b, 500c,... are capacitively coupled to the two signal lines 27a, 27b, 27c,. For example, the reflective pixel electrode 50a is capacitively coupled to the signal lines 27a and 27b with a substantially equal area, and the adjacent reflective pixel electrode 50b is capacitively coupled to the signal lines 27b and 27c with a substantially equal area. For this reason, a luminance difference between a certain reflection pixel electrode and another reflection pixel electrode adjacent thereto is reduced, and crosstalk can be prevented. As a result, when the raster window 302 is displayed on the green halftone background 301 as shown in FIG. 6, the voltage applied to the pixel 303 adjacent below the window 302 displays the window more than before. Pixel 3 in other area without being affected by voltage
04 approaches the original voltage VP0 applied. Therefore, occurrence of vertical crosstalk at the end of the window 302 is prevented.

In order to uniformly capacitively couple one signal line to two pixel electrodes, for example, as shown in FIG. 3, one signal line 203 is connected between two pixel electrodes 201 and 202. It is also conceivable to arrange them. With such a configuration, the influence of the potential of the signal line 203 on the two pixel electrodes 201 and 202 via capacitive coupling can be averaged.

However, if the signal line 203 is not disposed so as to be completely covered under either the pixel electrode 201 or 202, the liquid crystal layer in the portion where the pixel electrode does not exist may be formed by the potential of the signal line 203 and the opposite potential. Will respond.
As a result, an undesired display is performed above the signal line 203. Therefore, the signal lines need not be arranged as shown in FIG. 3 but arranged so as to have a portion completely covered by only each of the plurality of pixel electrodes as in the above embodiment. That is, taking the pixel electrode 50b shown in FIG. 1 as an example, this pixel electrode 50b is connected to the signal line 2
It is necessary to overlap a region including the entire width of 7b1 with a region including the entire width of the signal line 27c2. Here, the total width of the signal line is the width of the signal line in a direction orthogonal to the column direction as illustrated.

The above-described embodiment is merely an example, and does not limit the present invention. For example, in the above embodiment, one pixel electrode and two signal lines are arranged to face each other. However, even if not only two but also three or more signal lines and one pixel electrode are arranged so as to face each other,
Similar functions and effects can be obtained. However, if the number of signal lines increases, the length of the signal lines increases, which leads to an increase in the wiring area. Therefore, it is usually preferable to reduce the number to three or less.

Although the present embodiment is directed to a reflection type liquid crystal display device, crosstalk can be prevented by applying the present invention to a transmission type liquid crystal display device. However, in a transmissive liquid crystal display device, a pixel electrode has a light-transmitting property, and when two or more signal lines are arranged under one pixel electrode, it is difficult to secure an aperture ratio. On the other hand, in the reflective liquid crystal display device as in the above embodiment, the pixel electrode is an opaque reflective pixel electrode, so even if a plurality of signal lines are arranged under one pixel, the aperture ratio is affected. Without doing so, a high-luminance display is possible.

[0030]

As described above, according to the liquid crystal display device of the present invention, the portion where one signal line faces only the pixel electrode and the portion where only one pixel electrode faces only the other pixel electrode via the insulating film. Therefore, capacitive coupling is performed between the pixel electrodes and a plurality of pixel electrodes, and a luminance difference between the pixel electrodes can be reduced to prevent crosstalk.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure in a planar direction of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a longitudinal sectional structure along the line AA in FIG. 1;

FIG. 3 is a plan view showing a state in which one signal line is arranged between two pixel electrodes in a liquid crystal display device.

FIG. 4 is a cross-sectional view showing a structure of a conventional liquid crystal display device in a plane direction.

FIG. 5 is a sectional view showing a longitudinal sectional structure along the line BB of FIG. 1;

FIG. 6 is an explanatory diagram showing a window displayed on a screen and a peripheral area thereof.

FIG. 7 is a time chart showing a temporal change of a signal voltage applied to a pixel electrode of a conventional liquid crystal display device.

[Explanation of symbols]

20 Array substrate 22, 132 Substrate 24, 240 Scan line 26 Signal storage capacitor line 27a, 27a1, 27a2, 27b, 27b1, 27
b2, 27c, 27c1, 27c2 Signal line 29 Contact 30a, 30b, 30c, 300a, 300b, 300
c TFT 50a, 50b, 50c, 500a, 500b, 500
c Reflective pixel electrode 52 Color filter 54 Common electrode 80 Counter substrate 90 Liquid crystal layer 118 Insulating layer 188 Optical film 200 Liquid crystal display

Claims (4)

[Claims] A pixel electrode having a switching element on a substrate is arranged in a matrix, a plurality of signal lines are arranged in a column direction, and the switching element is commonly connected to each signal line for each column. An array substrate, a counter substrate disposed to face the array substrate, and provided with a light-transmitting counter electrode on the substrate, and a liquid crystal layer sandwiched between the array substrate and the counter substrate. In the liquid crystal display device, each signal line is alternately covered along a column direction with a pixel electrode connected to the signal line and a pixel electrode connected to a different signal line. apparatus. 2. The liquid crystal display device according to claim 1, wherein said pixel electrode is an opaque reflective electrode. 3. A pixel electrode having a switching element on a substrate is arranged in a matrix, a plurality of signal lines are arranged in a column direction, and the switching element is commonly connected to each signal line for each column. An array substrate, a counter substrate disposed to face the array substrate, and provided with a light-transmitting counter electrode on the substrate, and a liquid crystal layer sandwiched between the array substrate and the counter substrate. In a liquid crystal display device, each pixel electrode overlaps with a plurality of signal lines, and a region of the signal line overlapped with the pixel electrode is a region including the entire width of the signal line. 4. The liquid crystal display device according to claim 3, wherein the area where each signal line overlaps the pixel electrode is substantially equal.